Timing relay



Jan. 19, 1943. E L 'HARDER 2,309,066

I TMING RELAY Filed Dec. 22', 1958 ATTORNEY Patented Jiu. `'19,1943

TIHING RELAY dwinL.

'Weating Harder, Forest Bills, Pa., aslignor to house Electric Manufacturing Company, East Pittsburgh, Pa., a corporation Pennsylvania application neeemberz, 193s. serial :10.241.211

zwi claims. r(ci. `rus-.294)

My invention relates to electrical timing relay mechanisms, and it has particular relation to auch mechanisms operating on direct-current energizing-circuits, tor producing accurate timing for periods ranging from 950 of a second to y; of a second, more or less.

Heretofore time-delays of the shorter values,

' such as from l to 2 cycles on a 60-cycle system,

have been attained by interposing an auxiliary relay having a speed of operation approximately equal to the desired time-delay. For time-delays o! 55 second or longer, there have been available various motor-driven filled the requirements very nicely. However, for the intermediate timing periods, between about 1 or 2 cycles and something of the order oi 10 to 30 cycles, on a 60-cycle basis, timing equipment has heretofore had to rely largely on slow-pick-up direct-current relays, or relays having a short-circuited slug or washer placed on the magnetizable core, for delaying the rate of flux-build-up by reason of the eddy currents in the slug. These slow-pick-up relays have had various disadvantages, usually requiring operation on the drop-out movement oi the relay, being somewhat sensitive to changes in the battery-voltage in respect to their pickup times, and in any event operating at a time when the flux is changing slowly, thus causing considerable time-variations with comparatively small changes in the relay armaturetravel or gap, and with comparatively small changes in friction or in spring-adjustment.

An object of the invention is to utilize the principle oi a saturable inductance device, energized from a the property'oi developing a rapid rate of change of current during the period when the indctance device is saturating, that is, during the period between the non-saturated range oi ilux-densitives and the saturated range of nuit-densities.

A further object of my invention is to provide means for utilizing a non-linear current-limiting or voltage-limiting resistor, or both, in connection with my invention, in overcoming the deleterious effect of variable-voltage conditions on the timing.

A further object of my invention is to provide a relaying mechanism which is capable of causing a normally open contact to close at the end of a predetermined time after a circuit-making switching-operation, said predetermined time being within the previously mentioned timingrange.

With the foregoing and other objects in view, my invention consists in the circuits, apparatus,

timing devices which have direct-current circuit, and having methods and systems hereinafter described and claimed.. and illustrated in the accompanying drawing, wherein:

Figure 1 is a diagrammatic view-oi circuits and apparatus illustrating my invention in one form oi embodiment; v

Fig. 2 is an approximate curve-diagram with a superimposed diagram oi the equivalent circuit, illustrating the nature of the current-changes, with time, obtainable with the apparatus shown in Fig. 1;

Figs. 3 and 4 are views similar to Figs. 1 and 2, respectively, illustrating a modiilcation;

Figs.' 5 and 6 are also views similar to Figs. 1 and 2, respectively, illustrating a still further modification; and

Figs. 7, 8 and 9 are diagrammatic views illustrating the application oi non-linear resistors in accordance with my invention.

In Fig. 1, my invention is illustrated in connection with a direct-current energizing-circuit indicated by the positive-and negative terminals and energized by a storage-battery I0. My relaying mechanism comprises a normally open main controlling or initiating relay-contact II, an ordinary overcurrent relay I2, and a saturable inductance device I3. In the particular form oi invention shown in Fig. 1, the saturable inductance device I3 is a two-winding transformer comprising a primary winding Il and a secondary winding I5 mounted upon a common saturable ferro-magnetic core I6. The primary winding Il of the saturable inductance device is connected in series-circuit relation with the operating winding of the overcurrent relay I2 and with the initiating or controlling contact II, in an electrical circuit which is energized across the battery-terminals and The overcurrent relay I2 may have eithe/r a normally open iront or "make" contact I1, or a normally closed back or break contact I8, or both. A variable portion of the secondary winding I6 of the saturable inductance device I3 may be loaded with a resistance I8 which may be varied from various low values up to innity or open-circuit condition.

The equivalent circuit for the apparatus thus far described is indicated in the diagram in Fig.

2, wherein the battery-voltage is designated as E, the entire primary-circuit resistance is designated as Rp which includes the equivalent resistances of both the relay I2 and the primary winding I4, the corresponding equivalent secondarycircuit resistance is designated as R., the mutual reactance is designated as a purely inductive impedance Z, and the primary, secondary and magnetizing currents ane designated as I, I. and Iz, respectively.

When such a circuit is iirst closed. at a moment corresponding to zero time in Fig. 2, the current quickly rises to a steady value of approximately 'I'his equation assumes, in accordance with the facts, that the magnetizing current Iz through the reactance Z is negligibly small in comparision with the secondary current I..

From the equivalent diagram in Fig. 2, it will be noted that the voltage LR. is impressed upon the reactance of the saturable inductance device. This voltage will cause the magnetizing current Iz to begin to build up in this inductance device at a rate such that the induced voltage, which is induced by the rate of change of the magnetic iiux in the inductance device, is just equal and opposite to the impressed voltage LR..

The inductance device Il may be visualized as a 100-henry choke-coil, or as a 1000-volt transformer. except that it would be insulated tor more like 100 volts rather than 1000 volts, although I am obviously not limited to any particular values. Considering an inductance device which, on 60-cycle excitation, would develop 1000 volts RMS (root-means-square) across its primary winding I4, the ratio between this RMS voltage and the average voltage for a quarter of a cycle would be This average voltage is the voltage which is induced when the magnetic induction is changed from zero to its maximum operating value, which is llust under the knee of the saturationcurve, in an ordinary transformer-design. Therefore, such an inductance device would produce an average of 1000/1.11 volts in 1/4 of a cycle or 1,540 second.

If we assumed that we could make use of a fluxchange from a negative maximum value of magnetic induction to a positive maximum value of magnetic induction, this average voltage oi 1000/1.11 would be maintained for 1/120 second, or a quantity equal to l/120X 1000/1.11 or 7.51 volt-seconds. A

If we assume a battery-voltage which is normally rated at 125 volts, but which, as a matter of fact, varies between a somewhat higher value and a somewhat lower value, and if we further assume that an average of 35 volts is consumed in the reactance Z, which means that R..I.=35, then the above-mentioned inductance device would maintain an average of 35 volts for 7.51/35 ..215 second or 12.9 cycles. The foregoing discussion covers the time from up to the point 21 in Fig. 2.

During the period when the magnetizable core of the inductance I3 is saturating, the rate oi change of the magnetizing current Iz in the inductance device must rapidly increase, in order to induce a given voltage in the inductance device, until ilnally, when the magnetic circuit is wholly saturated, as indicated at 22 in Fig. 2, practically no voltage is induced in the induction device, no matter how rapidly the magnetizing current Iz increases. Under these fully-saturated conditions, the direct current ilows freely through the pure reactance Z in the equivalent diagram shown in Fig. 2, with a practically zerovoltage drop therein, so that the secondary current reaches a value In=0, while the primary current reaches a value It will be noted that, during the transitionperiod, while the induction device is saturating, or in the vicinity of the knee oi the saturationcurve, the primary current increases in the ratio which can be adjusted by the proper choice of the primary and secondary resistances Re and R..

According to my invention, the overcurrent relay I2 is so chosen or designed, that it has a pickup value intermediate between the non-saturated primary current Ip; and the saturated primary current 1pz. as indicated by the 'dotted line 22 in Fig. 2, thus giving a time oi operation from 0 to theline24in1iig.2.1twillbenotedthatthis time o! operation is ixed by the constants of the electrical circuit, depending upon the saturation of the inductance device I2 and depending also upon the pick-up current-value 2l of the relay I2. Referring, again, to Fig. 1, it will be noted that I have provided means for normally saturating the inductance device I3 in a polarity opposite to the polarity in which it is saturated during operating conditions. The means which are shown for this purpose, in Fig. 1, include an auxiliary circuit 2l which energizes the secondary winding Il from the battery Il through a large resistance 26, so as to limit the exciting current to a properly small value. It will be noted that the primary and secondary windings I4 and I5 are provided with polarity marks X to indicate corresponding terminals, and it will be further noted that the prepolarizing circuit 25 normally energizes the inductance device so .that it is saturated with the positive battery terminal connected to the marked secondary terminal, whereas, when the main controlling contact II closes, the primary circuit is energized so that the marked primary terminal is connected to the negative battery terminal Thus, when the primary circuit is established, the magnetic iiux in the inductance device changes, from its normal maximum saturating value in one polarity, to the maximum saturating value in the opposite polarity, thus taking advantage of the maximum possible flux-change in the inductance device, a mix-change which is fixed and constant, regardless oi such considerations as residual magnetism or battery-voltage. In the foregoing explanation of the conditions shown in Figs. 1 and 2, it will be noted that the secondary resistance R. might well be infinity, which means that the secondary circuit would be open-circuited. Such a condition is depicted in Fig. 3, wherein the relay I2 is energized, from the battery terminals and in an energizing circuit serially including the initiating contact I I and an adjustable number o1' turns of a saturable inductance-device 28, the circuit being completed through a primary resistor 28, which may be of very small value, or may be omitted entirely, if desired. In the apparatus shown in Fig. 3, an auxiliary pre-saturating circuit may be traced through the whole of the induction device 28 and through two large resistors 3| and 32, which normally draw a very small charging-current from E Ivg-E Y the battery terminals and As shown in Fig. 4, the equivalent circuit for the apparatus oi' Fig. 3 includes the equivalent primary resistance Rp and the inductance Z, without any secondary circuit at all. The initial non-saturated primary current Ipi is substantially zero, being merely the value of the almost negligibly small magnetizing current. When saturating conditions are reached, the primary current I rapidly increases in value until, at full saturation, it reaches its steady-state value 172 :E The relay I2 is set to have a pick-up value 23 somewhere along the slope of Ip during the saturating conditions of the inductance device, giving a pick-up time as determined by the line 24.

It will :be noted, from 2, that during the saturating period, I obtain not only a rapid increase in the primary current Ip, -but also a rapid decrease in the secondary current Ia. It is possible, therefore, to utilize a relay, as depicted in Fig. 6, having a pick-up value 34 which is some what below the initial value of the secondary current Isi. and having a relay drop-out value 35 which falls within the range of the rapidly decreasing secondary current L] during the saturating period of the operation, thus giving a total time to relay drop-out, from O to the line 35 in Fig. 6. Under these conditions, it is obvious that the relay would have to be included in the secondary circuit of the inductance device or, reierring to the equivalent circuit, in shunt-circuit relation to the inductance Z of the inductance device.

Fig. 5 shows an example of circuits and apparatus embodying the invention as depicted in Fig. 6. In Fig. 5, the primary energizing-circuit cornprises simply the operation-initiating contact I I in series with the primary winding 38 of a saturable inductance device 33 which is shown as having an iron core 40 provided witha small air-gap 4I therein and provided also with a secondary winding 42. An under-current relay 43 is energized across an adjustable portion of the secondary winding 42. The air-gap 4I is a small gap, perhaps of the order of mils in length, which is very small compared to the size of gap which would be necessary to prevent saturation of the iron core 40 under the operating conditions of the device. The small gap 4I serves the purpose of causing the residual magnetic induction to reduce substantially to zero when the inductance device 39 is deenergized by the opening of the initiating contact I I after each operation of the timing mechanism. In this embodiment of my invention, I utilize only the iluxchange from zero to the maximum saturating value in the operating direction, instead of utilizing the double amount of flux-change which has been explained in connection with Figs. l to 4. This avoids the necessity for having a constantly energized, pre-saturating circuit such as the circuit --26 in Fig. l or the circuit 3 I'-32 in Fig. 3.

One phase of my invention relates to thedesirability of obtaining a timing-relay make contact which closes in a predetermined short time, such as 13 cycles, or other adjustable time, after the closure of a main operation-initiating contact II. In Figs. 1 and 3, such a time-delay "make contact is provided, in the form of the make-contact I1 of the overcurrent relay I2, which does not pick up until the time 24 has been reached, as indicated in Figs. 2 and 4, respectively.

In Fig. 5, the undercurrent relay 43 is shown as being provided with a make-contact 41 and a break-contact 43. The make-contact 41 is closed, however, almost instantly after the closure of the operation-initiating contact Il, and

this make-contact 41 remains closed until the relay drop-out time 36 is reached, as depicted in Fig. 6. In order to obtain a-contact which is not made until the make-contact 41 of the undercurrent relay 43 drops out, I have shown, in Fig. 5, an auxiliary relay-element 50 comprising an electromagnet 5I and a cooperative pivoted armature 52, which normally rests against a.

backstop 53, and which carries a spring-member 54 the end of which is weighted with an inertiamass 55. This auxiliary relay 50 is provided with a controlled circuit 55 including a stationary contact-member 51 which is normally spaced from the resilient spring-part 54 of the movable element of the relay.

In the operation of the auxiliary relay-element 50 of Fig. 5, the closure of the make-contact 41 energizes the auxiliary relay-element 50 and causes the armature 52 to pick up, moving away from its backstop 53. Under these circumstances, the circuit 55 continues to be open-circuited at 51. When the front contact 41 of the under-current relay 43 finally opens, the auxiliary relay-element 50 is deenergized, permitting the movable armature '52 to drop back to its backstop 53, and the inertia of the mass 55 will cause it to continue to move until the spring-part 54 makes contact with the electrical contactmember 51, thus completing the circuit 56 in a time which is controlled by the saturating characteristics of the inductance device 39.

A disadvantage common to all battery-energized timing-relay mechanisms is that any variation in the battery-voltage is quite likely to have a more or less deleterious effect upon the timing period. This deleterious effect is not as large, in my hereinabove-described devices, as in other, 0r prior-art devices, because of the rapid change in current which I obtain atthe operating point of the relay.

In order to still further minimize the deleterious effects of voltage-changes in the directcurrent energizing circuit, I preferably make use of a non-linear resistor, as is illustrated in several different forms of embodiments in Figs. 7 to 9. Several such non-linear resistors are known on the market, and they include resistors of the current-limiting, or so-called constantcurrent, type, having the property of increasing theirresistance when the applied voltage is increased, as exemplined in a ballast resistance or a tungsten lamp. Other non-linear resistors on the market are of the voltage-limiting, or socalled constant-voltage, type, having the property of decreasing their resistance as the current increases, as exemplied in so-called voltageregulating tubes, glow-lamps, the forwardcircuit characteristics of copper-oxide rectiflers, and certain composite lightning-arrester materials.

Reference to the equivalent-circuit diagram in Fig. 2 will show that the voltage impressed on the equivalent reactance Z of the inductance device is the secondary voltage-drop LR. The rate at which the magnetizing current Iz builds up is dependent, therefore, upon this secondaryvoltage, and this voltage is dependent, in turn, upon the battery-voltage E. It will be obvious that, if the secondary resistance Re is of a nature tending to hold its voltage-drop IRa constant, or if it even approaches such a characteristic, such a secondary resistance will counteract or minimize the effect of a variable battery-voltage E upon the time required for the inductance device to reach the knee of its saturation curve as indicated by the line 2| in Fig. 2.

In like manner, also, it will be seen, from the equivalent-circuit diagram of Fig. 2, that if the equivalent primary resistance R., were of a nature tending to hold the current constant, that is, if'it increased its resistance when the battery-voltage E increased, there would be a more nearly constant voltage-difference (E-IpRp) =IR|, so that the saturation buildup-time would be more nearly constant, by reason of the more nearly constant voltage ISR, impressed upon the equivalent reactance Z of the inductance device.

Fig. 7 shows an exemplary form of embodiment of my invention, including the principles just discussed. The primary circuit, as before, is a battery-energized circuit and it includes the normally open operation-initiating contact Il, the primary winding i4' of a saturable inductance device S3, the overcurrent relay I2, and a nonlinear current-limiting resistor 64. The saturable inductance device 63 is provided with a secondary winding I5' which energizes the undercurrent relay 43 and a serially connected nonlinear voltage-limiting resistor i5. The saturable inductance device 63 is further provided with a tertiary winding S6 which is utilized for giving the inductance device an initial saturating flux in the direction opposite to the direction or polarity at which it saturates when the primary circuit is energized, said tertiary winding O6 being in a battery-energized circuit including a current-limiting resistor G1. o

While I have shown, in Figs. l, 3, 5 and 7, four different arrangements or embodiments of the saturable inductance device, as indicated at Il, 2l, 39 and 63, it will be obvious that any one of these inductance devices may be substituted for any of the others, and it will be further obvious that any of the elements of any of the circuits may be omitted, if the functions o! said elements are not needed or desired, or if said functions are dispensed with in the interest of obtaining a better performance of the rest of the equipment.

In Figs. 8 and 9, I illustrate two other circuitarrangements for advantageously counteracting, or partially counteracting, the deleterious effects of variations in the battery-voltage, with the aid of a current-limiting resistor M' or a voltagelimiting resistor i5', respectively.

In Fig. 8, the current-limiting resistor I4 is included in a primary battery-energized circuit which serially includes the initiating contact Il and another resistance-element 1I, so that the current-regulating properties of the non-linear resistor 64 tends to maintain a fairly constant current in the resistance 10, independently of the battery-voltage, thus resulting in a substantially constant voltage-drop across the resistance 1l. This substantially constant voltage-drop is utilized as a source of voltage for energizing a timing relay mechanism of a type in which the time of response depends upon the impressed voltage. A simple form of such timing relay mechanism is illustrated, in Fig. 8, in the shape of an overcurrent relay i2' and a serially connected saturable inductance device 2l.

In Fig. 9, the voltage-limiting resistor Il' is included in a primary battery-energized circuit including the initiating contact Il and another resistance 1i, so that the voltage-regulating properties of the non-linear resistor 65 tends to maintain a substantially constant voltage across its terminals, independently oi' variations in the Cil battery-voltage. 'nais substantially constant voltage across the voltage-limiting resistor il is utilized as a source of energy for a timing relay mechanism auch as the mechanism I22l of Fig. 8.

While I have illustrated my invention in a number of diti'erent forms of embodiment, I wish it to be understood that the specinc forms are intended to be merely illustrative of the principl of the invention, as my invention, in its broader aspects, is obviously not limited to these particular forms, but various substitutions, omissions and additions may be made by those skilled in the art without departing from all of the essential features o! the invention. I desire, therefore, that the appended claims shall be accorded the broadest construction consistent with their language and the prior art.

I claim as my invention:

l. A timing relay mechanism comprising, in combination, a direct-current energizing-circuit, a saturable inductance device, a normally open circuit-controlling switching-means for, at times, causing said inductance device to become energized solely from said direct-current energizingcircuit, a direct-current relay-element, and means for causing said relay-element to be so energized as to be responsive to tlux and current-changes during the period when said inductance device is saturating, said circuit-controlling switching-means operating to causel said inductance device to be connected to said directcurrent energizing circuit prior to the response of said relay-element, and the magnetizing current of said inductance device prior to the saturation thereof being a small fraction of the relaycurrent at the moment when said relay makes its aforesaid response.

2. A timing relay mechanism comprising, in combination, a direct-current energizing-circuit, an inductance device having a saturable ferromagnetic core having a small air-gap therein, a normally open circuit-controlling switchingmeans for, at times, causing said inductance device to become energized solely from said directcurrent energizing-circuit, a direct-current relay-element, and means for causing said relayelement to be so energized as to be responsive to tlux and current-changes during the period when said inductance device is saturating.

3. A timing relay mechanism comprising, in combination, a direct-current energizing-circuit, a saturable inductance device, means for causing said inductance device to be normally saturated in one polarity of magnetic ilux, a normally open circuit-controlling switching-means for, at times, causing said inductance device to be connected to said direct-current energizing-circuit in such direction of energization that said inductance device after a time becomes saturated in the opposite polarity of magnetic ilux, a direct-current relay-element, and means for causing said relayelement to be so energized as to be responsive to flux and current-changes during the period when said inductance device is saturating in said opposite polarity.

4. A timing relay mechanism comprising, in combination, a direct-current energizing-circuit, a saturable inductance device, circuit-controlling means associated with said direct-current energizing-circuit for normally causing said inductance device to be saturated in one polarity of magnetic ilux and for, at times,l causing said inductance device to become saturated in the opposite polarity oi magnetic iiux, a direct-winnt ascaooc relay-element, and means for causing said relayeiement to be so energized as to lic-responsive to ilux and current-changes during the period when said inductance device is saturating in said opposite polarity.

5. A timing relay mechanism comprising, in combination, a direct-current energizing-circuit, a saturable inductance device, a direct-current relay-element, and a normally open circuit-controlling switching-means for, at times, causing said inductance device and said relay-element to be connected in series-circuit relation to each other in an electrical circuit which is energized from said direct-current energizing-circuit, said relay-element having a pick-up current-value corresponding to operating conditions obtaining during the period when said inductance device is saturating, said circuit-controlling switchingmeans operating to cause said inductance device to be connected in its energized circuit prior to the response of said relay-element, and the magnetizing current of said inductance device prior to the saturation thereof being a small fraction of the relay-current at the moment when said relay makes its aforesaid response.l

6. A timing relay mechanism comprising, in combination, a direct-current energizing-circuit, an inductance device having a saturable ferromagnetic core having a small air-gap therein, a direct-current relay-element, and a normally open circuit-controlling switching-means for, at times, causing said inductance device to be connected in an electrical circuit which is energized solely from said direct-current energizing-circuit, and means for causing said relay-element to be so energized as to be responsive to flux and current-changes during the period when said inductance device is saturating.

'7. A timiug relay mechanism comprising, in combination, a direct-current energizing-circuit, a saturable inductance device, meansfor causing said inductance device to be normally saturated in one polarity of magnetic ilux, a direct-current relay-element, and a normally open circuit-controlling switching-means for, at times, causing said inductance device and said relay-element to be connected in series-circuit relationto each other in an electrical circuit which is energized from said direct-current energizing-circuit in such direction of energization that said inductance device after a time becomes saturated in the opposite polarity of magnetic flux, said relay-element having a pick-up current-value corresponding to operating conditions obtaining during the period when said inductance device is saturating in said opposite polarity.

8. A timing relay mechanism comprising, in combination, a direct-current energizing-circuit, a saturable inductance device, electric-circuit means including current-limiting resistance for causing said inductance device to be normally energized from said direct-current energizingcircuit so as to be normally saturated in one polarity of magnetic ux, a direct-current relayelement, and a normally open circuit-controlling switching-means for, at times, causing said inductance device and said relay-element to be connected in series-circuit relation to each other in an electrical circuit which is energized from said direct-current energizing-circuit in such direction of energization that said inductance device after a time becomes saturated in the opposite polarity of magnetic ilux, said relay-element having a pick-up current-value corresponding to operating conditions obtaining during the period when said inductance device is saturating in said opposite polarity.

9. A timing relay mechanism comprising, in

combination, a direct-current energizing-circuit, a saturable inductance device, a normally open circuit-controlling switching-means for, at times, causing said inductance device to become energized solely from said direct-current energizingcircuit, a direct-current relay-element, and means for causing said relay-element to be energized in shunt-circuit relation lto said inductance device, said relay-element having a drop-out current-value corresponding to operating conditions obtaining during the period when said inductance device is saturating. l

10. A timing relay mechanism comprising, in combination, a direct-current energizing-circuit, an inductance device having a saturable ferromagnetic core having a small air-gap therein, a normally open circuit-controlling switchingmeans for, at times, causing said inductance de-l vice to become energized solely from said directcurrent energizing-circuit, a direct-current relay-element, and means for causing said relayelement to be energized in shunt-circuit relation to said inductance device, said relay-element having a drop-out current-value corresponding to operating conditions obtaining during the period when said inductance device is saturating.

11. A timing relay mechanism comprising, in combination, a direct-current energizing-circuit, a saturable inductance device, means for causing said inductance device to be normally saturated in one polarity of magnetic flux, a normally open circuit-controlling switching-means for, at times. causing said inductance device to be connected to said direct-current energizing-circuit in such direction oi' energlzation that said inductance device after a time becomes saturated in the opposite polarity of magnetic ilux, a direct-current relay-element, and means for causing said relayelement to be energized in shunt-circuit relation to said inductance device, said relay-element having a drop-out current-value corresponding to operating conditions obtaining during the period when said inductance device is saturating.

12. A timing relay mechanism comprising, in combination, a direct-current energizing-circuit, a saturable inductance device, electric-circuit means including current-limiting resistance for causing said inductance device to be normally energized from said direct-current energizingcircuit so as to be normally saturated in one polarity of magnetic flux, a normally open circuitcontrolling switching-means for, at times, causing said inductance device to be connected to said direct-current energizing-circuit in .such direction of energization that said inductance device after a time becomes saturated in the opposite polarity of magnetic ilux, a direct-current relayelement, and means for causing said relay-element to be energized in shunt-circuit relation to said inductance device, said relay-element having a drop-out current-value corresponding to operating conditions obtaining during the period when said inductance device is saturating.

13. The invention as dened in claim 1, characterized by means including la non-linear current-limiting resistor for minimizing the eilects ot voltage-changes in said direct-current energizing-circuit.

14. The ,invention as dened in claim 5 characterized by a non-linear current-limiting re-l 15. The invention as defined in claim 9, charaoterized by a non-linear current-limiting resistor connected in series-circuit relation to said inductance device.

16. The invention as defined in claim 1, characterized by said direct-current energizing-circuit being tapped off of a relatively constantvoltage element of a primary circuit comprising, in series, a source of variable unidirectional voltage, a relatively iixed-value resistor, and a nonlinear resistor which is responsive to an electrical condition of said circuit.

17. The invention as defined in claim l, characterized by means including a non-linear voltage-limiting resistor for minimizing the efi'ects of voltage-changes in said direct-current energizing-circuit.

18. The invention as defined in claim 5, char-e acterized by a non-linear voltage-limiting resistor connected in shunt-circuit relation to said inductance device.

19. The invention as defined in claim 9, characterized by a non-linear voltage-limiting resistor connected in series-circuit relation to said relayelement.

20. The invention as dened in claim 1, characterized by said direct-current energizing-circuit being tapped oil' of a non-linear voltage-limiting resistor of a primary circuit comprising, in series, a source of variable unidirectional voltage, said non-linear voltage-limiting resistor, and another resistance-element.

21. A timing relay mechanism comprising, in combination, a primary circuit comprising, in series, a source of variable unidirectional voltage, a non-linear resistor which is responsive to an electrical condition of said circuit, and another resistor of a dissimilar nature; timing-relay means tapped off of a relatively constant-voltage element of said primary circuit, said timing-relay means being of a type which performs a relaying function after a predetermined time-interval following the application of voltage thereto, said time-interval being dependent somewhat upon the voltage; and means for initiating the application of said voltage to said timing-relay means.

22. A timing relay mechanism comprising. in combination, a primary circuit comprising. in series, a source of variable unidirectional voltage, a non-linear voltage-limiting resistor, and another resistance-element: timing-relay means tapped off of said non-linear voltage-limiting resistor, said timing-relay means being of a type which performs a relaying function after a predetermined time-interval following the application of voltage thereto, said time-interval being dependent somewhat upon the voltage; and means for initiating the application of said voltage to said timing-relay means.

23. The invention as denned in claim 9, characterized by said relay-element having a "make" contact; in combination with a second relay-element having a normally open back-contact and having an inertia-mass so carried by its movable element that said second relay-element has the property of closing its normally open back-contact on the back-stroke resulting from the deenergization of the relay-element after having been energized. and means for causing said second relay-element to be energized during the period of closure of said "make contact of the first-mentioned relay-element.

24. Means for effecting the closure of a normalLv open contact after a predetermined timeinterval following the closure of an electrical circuit, comprising the combination, with said electrical circuit and means for eifecting said closure thereof, of relay-means responsive to the closure of said circuit for causing an auxiliary contact to close and to thereafter remain closed for a predetermined time and to open at the expiration of said time, a relay-element having a normally open back-contact and having an inertia-mass so carried by its movable element that said relayelement has the property of closing its normally open back-contact on the back-stroke resulting from the deenergization of the relay-element after having been energized. and means for causing said relay-element to be energized during the Deriod of closure of said auxiliary contact.

. EDWIN L. HARDER 

